Our ultimate goal is to understand the molecular basis of the process of visual phototransduction performed by visual pigments. Our approach is to solubilize and purify rhodopsin from both vertebrate and invertebrate and then to reassemble it into model lipid bilayers that allow measurements that are not readily achieved otherwise. Rhodopsin has been incorporated into planar bilayers which separate two aqueous compartments and are readily amenable for electrical measurements. Furthermore, asymmetric bilayers containing rhodopsin only on one monolayer are formed by apposing a lipid monlayer to a rhodopsin-lipid monolayer. The effect of light on this system is to induce the formation of a voltage-sensitive channel. The kinetics of channel opening and closing, and the ion-selectivity of the channel are under current investigation. Rhodopsin is also incorporated into bilayer vesicles, with diameters of several micrometers. The optical spectral properties of rhodopsin in the vesicles are similar to those recorded in retinal rod disc membranes by chemical, optical and electrical techniques.